Coil Relay Results Question

[mmattockx]

I did the coil relay mod last weekend on my 1100E. Previously it had 9.8-10.0V at the coils with a fully topped up battery. The thing started and idled very well and generally ran very well with none of the usual problems people attribute to low voltage at the coils. My battery is currently on the way out, so the coils were actually seeing more like 8.8-9.0V after it sat overnight and who knows how low as the starter pulled the battery down. Again, starting and idle were excellent even with the flaky battery.

After the mod I now have full battery voltage at the coils or at most 0.1V less . Took it for a test ride yesterday and it ran the same as before, instant starting, smooth idle and great running throughout the rev range. I'm not complaining about it or anything, but I am wondering just how much the problems that people blame on low voltage at the coils are really symptoms of other issues? How often do bikes run just fine with low voltage at the coils? My bike has coils and plug wires off a mid-90's GSXR600 if that matters any on the performance with low voltage.

Thoughts, experiences about this? Anybody else have a bike run good with less than optimal power to the coils?


Mark

[posplayr]

My 1100 was progressively getting worse in terms if how hard it was to start to the point I needed to use starter fluid if it sat for more than a few days. After the mod it would start instantly. Not saying this is everyone's problem but it can certainly cause a hard start.

[bearrocco]

Do the smaller bikes like an 82 gs550 have a coil relay , Or is that the igniter

[Steve]

NONE of the stock GSes have a coil relay.

That is a somewhat popular modification that is done to restore full power to the coils by bypassing the 'less than perfect' connections in the fuse box, ignition switch and wiring harness in general.

It has long been my philosophy that if the connections to the coil are suspect, so are the rest of them, so I have changed the fuse box and provided a relay that feeds the fuse box. That way, EVERYTHING gets fresh power.

.

[hillsy]

NONE of the stock GSes have a coil relay.

That is a somewhat popular modification that is done to restore full power to the coils by bypassing the 'less than perfect' connections in the fuse box, ignition switch and wiring harness in general.

It has long been my philosophy that if the connections to the coil are suspect, so are the rest of them, so I have changed the fuse box and provided a relay that feeds the fuse box. That way, EVERYTHING gets fresh power.

.

It's not just the connectors that increase resistance - wiring can increase in resistance over time and cause the same problem. Hence the relay mod with fresh wire straight from the battery terminal eliminates all this.

To the OP - your non stock coils may be of a different primary resistance and therefore throwing up a better spark in the first place, so the drop in voltage may not have been as noticeable in comparison to stock coils with lowered input voltage.

[geol]

If anyone has soldered original wiring, there are times when wires turn brown and don't want to hold solder as well. This old wire is oxidized and does indeed increase resistance. Old OEM coils or new and fresh aftermarket, the power going into the coils is multiplied and fires the plugs in the same proportion so 12V gives more spark than 9V. Keep track of your spark plugs after doing the coil mod. You will see that the plugs got a bit sooty prior and check your fuel mileage. It almost always goes up a little after then mod. With a big block strong engine, the engine may not feel a lot different otherwise. Another symptom of low coil voltage is odd/random backfire pops while cruising along at a set speed.

[bearrocco]

Where do I get this kit !?

[BigD_83]

Where do I get this kit !?

It's not a kit, per se. You just need some wire of appropriate gauge, some connectors, the ability to solder, a relay, and some basic electrical know-how.

I believe there is a Coil relay instructable on BassCliff's website.

[mmattockx]

Where do I get this kit !?

As noted, it isn't a kit. The basic idea is that you install a relay to take power directly from the battery or fuse box auxiliary power posts and run it straight to the coils, instead of letting the harness wiring supply the power to the coils. I can take a couple of pics of my set up if you want some idea of one way to do it. I didn't want to cut anything in the harness or solder on the harness wiring so I used bullet connectors to essentially insert the relay in between the harness power supply to the coils and the coils.

I think BigD_83 is correct that there is a write up on BassCliff's site: http://members.dslextreme.com/users/bikecliff/


Mark

[BigD_83]

Thanks for posting the link, Mark. I meant to go back to do that but ended up with a busy day at work, before heading out of town for the long weekend.

I'd be curious to see what you have done with your setup.

[mmattockx]

To the OP - your non stock coils may be of a different primary resistance and therefore throwing up a better spark in the first place, so the drop in voltage may not have been as noticeable in comparison to stock coils with lowered input voltage.

I believe they are 3-5 Ohm on the primary side, the same as the 1100E specs. I bought them because they were the correct match for the GS ignition system, but it was years ago and my memory may have dimmed some in that time. I guess I could go pull the tank and measure them just to know for sure.

You will see that the plugs got a bit sooty prior and check your fuel mileage. It almost always goes up a little after then mod.

My odometer doesn't work, so I don't have a definitive mileage number. Just before I did the mod I went on a ride that was a bit over 200km. I was fighting a 30kmh headwind on the way out and had to fill up part way back to be sure I made it home. I think I could have made it, but it would have been close. Today I did a similar route (not quite as long, but on the same roads), and went very close to 150km and used 1/2 a tank to do it, with no head wind this time. I would say I got a substantial mileage improvement.

I'd be curious to see what you have done with your setup.

I will get some pics when I pull the tank to measure the coil primary resistance, tonight or tomorrow.


Mark

[Grimly]

Thoughts, experiences about this? Anybody else have a bike run good with less than optimal power to the coils?


Mark

Mine (the GSs) always run with a slight ragged edged harshness when the coil voltage is less than optimal. Not something a strange rider would notice, but I'm aware of it. It's always gone away when the low tension feeds are cleaned and secured for another couple of years.

[mmattockx]

Mine (the GSs) always run with a slight ragged edged harshness when the coil voltage is less than optimal. Not something a strange rider would notice, but I'm aware of it. It's always gone away when the low tension feeds are cleaned and secured for another couple of years.

Interesting. I was thinking it was running a touch smoother on the ride today but just figured it was in my head because I wanted to believe the relay did some good. Maybe I wasn't imagining it then.


Mark

[mmattockx]

Thanks for posting the link, Mark. I meant to go back to do that but ended up with a busy day at work, before heading out of town for the long weekend.

I'd be curious to see what you have done with your setup.

Well, only 12 days later... Our weather has been crap the last couple weeks, with lots of rain so nothing much has been done. I have a free day today with the GF out of town so I pulled the tank and took some pics along with other tinkering.

I used a 40A relay and socket as available from my local Canadian Tire store. Cost was ~$15 for both pieces. I mounted the relay beside the fuse box using an empty mounting bolt location left behind when I installed an SH775 R/R. The main power comes from the auxiliary power terminals on the bottom of the fuse box (thanks to posplayr for this idea). This is a 10A fused circuit that is hot all the time, key on or off. The harness wiring at the coil end is Orange/White supplying 12V to the '+' side of the coils from the harness. These wires only go hot when the key is on and the ignition is hot, so I used one of them as the trigger supply for the relay. I unplugged both O/W wires from the harness (there are bullet connectors between the harness and the coils), plugged the signal wire for the relay into one of the harness O/W wires and then ran power from the relay up to the coils in one wire, splitting it near the end to plug into both coil power inputs. I used standard 0.157" bullet connectors and they worked fine with the OEM Suzuki connectors (which I think are 4mm). I tweaked one on my female connectors with pliers to get it just right and the other one was fine as it came. All my wiring is 18ga primary wire, nothing fancy. The 18ga is good for ~15ft of length at the maximum 10A current that circuit can supply so I didn't bother with anything heavier. As noted earlier in the thread, my coils and plug wires are from a mid-90's GSXR600. They bolt straight up to the GS coil mounts and everything fits like it was made for the GS.


Fusebox pic. Yellow and black are the signal and power output leads from the relay:



View inside the airbox area. You can see the black and yellow wires coming around from behind the R/R and connecting to the black and red wires piggybacked onto the harness. Black is signal and red is power:



View up the chassis, you can see the black and red wires running up the harness (LH side of the bike) towards the coils:



View of the coils. You can see the red power wire splitting into two and connected to the coil side O/W wires and the black signal wire plugged into the harness side O/W wire:



I have an update on the mileage, too. Despite the weather I got out a bit more and got almost exactly 250km of mostly highway riding (110-120km/h) on a full tank before hitting reserve. I don't recall my mileage from the dim past, but I don't think I ever got close to 250km to a tank before. I call this a solid win just for the mileage improvement if nothing else.


Mark

[jabcb]

Something else to think about when you have the bike apart & the tools out for the ignition relay mods.


You can do something similar to the headlight circuit to get a brighter headlight.